Ims and Method of Multiple S-Cscf Operation in Support of Single Puid

1. A method for providing multimedia services to subscriber user equipment within an internet protocol multimedia subsystem network, comprising: configuring the internet protocol multimedia subsystem network to provide a single subscriber user equipment with a capability of fork registering with multiple serving-call session control functions, wherein the configuring includes setting a multiple serving-call session control function forking data field for the single subscriber user equipment maintained by a home subscriber server; and wherein: the single subscriber user equipment signals to fork register with a proxy call session control function; the proxy call session control function signals to register with an interrogating call session control function; the interrogating call session control function signals the home subscriber server, the home subscriber server responds by determining whether the single subscriber user equipment is already registered, and whether the single subscriber user equipment is enabled to fork register to multiple serving-call session control functions, and signals the interrogating call session control function with eligible serving-call session control function capabilities if the multiple serving-call session control function forking data field is set; and the interrogating call session control function responds by choosing the multiple serving-call session control functions from eligible serving-call session control functions, and register signalling the chosen, eligible multiple serving-call session control functions.

2. The method as set forth in claim 1 , further comprising: after obtaining internet protocol connectivity, the single subscriber user equipment signalling to register onto the internet protocol multimedia subsystem network; and the internet protocol multimedia subsystem network responding by fork registering the single subscriber user equipment to multiple eligible serving-call session control functions.

3. The method as set forth in claim 1 , further comprising: the chosen multiple serving-call session control functions exchange signalling with the home subscriber server; the home subscriber server recording a binding fork registration and sending subscriber user equipment profile information to each of the multiple fork registered serving-call session control functions; each of the multiple fork registered serving-call session control functions responding by signalling the interrogating call session control function; the interrogating call session control function responding by signalling the proxy call session control function with registration information, and the proxy call session control function responding by creating security associations and storing a list of the multiple fork registered serving-call session control functions.

4. The method as set forth in claim 3 , further comprising: the single subscriber user equipment using an algorithm to choose one of the security associations with the proxy call session control function and its associated registered serving-call session control functions in response to an outgoing call from the single subscriber user equipment.

5. The method as set forth in claim 4 , further comprising: if one of the multiple fork registered serving-call session control functions is determined by the single subscriber user equipment or the proxy call session control function to be unavailable for the outgoing call, the single subscriber user equipment choosing an alternative one of the security associations to reach an alternate fork registered serving-call session control function.

6. The method as set forth in claim 3 , further comprising: the interrogating call session control function using an algorithm to choose one of the multiple fork registered serving-call session control functions in response to an incoming call to the single subscriber user equipment.

7. The method as set forth in claim 6 , further comprising: if one of the multiple fork registered serving-call session control functions is determined by the internet protocol multimedia subsystem network to be unavailable for the incoming call, the interrogating call session control function choosing an alternative one of the multiple fork registered serving-call session control functions.

8. A non-transitory computer readable medium storing computer program instructions for providing multimedia services to subscriber user equipment within an internet protocol multimedia subsystem network, which, when executed on a processor, cause the processor to perform operations comprising: configuring the internet protocol multimedia subsystem network to provide a single subscriber user equipment with a capability of fork registering with multiple serving-call session control functions, wherein: after obtaining internet protocol connectivity, the single subscriber user equipment register signals the internet protocol multimedia subsystem network; and wherein the internet protocol multimedia subsystem network fork registers the single subscriber user equipment to multiple serving-call session control functions; and setting a multiple serving-call session control function forking data field and eligible serving-call session control functions maintained by a home subscriber server for the single subscriber user equipment; wherein: the single subscriber user equipment signals to register with a proxy call session control function, the proxy call session control function register signalling an interrogating call session control function; the home subscriber server determines whether the single subscriber user equipment is already registered, and whether the single subscriber user equipment is enabled to fork register; the home subscriber server signals the interrogating call session control function with eligible serving-call session control function capabilities if the single subscriber user equipment is fork register enabled; and the interrogating call session control function selects the multiple serving-call session control functions from the eligible serving-call session control functions and register signals the chosen, eligible multiple serving-call session control functions.

9. The non-transitory computer readable medium as set forth in claim 8 , the computer program instructions further comprising: the chosen multiple serving-call session control functions responding by exchanging signals with the home subscriber server; the home subscriber server responding by recording a binding fork registration in the home subscriber server and sending subscriber user equipment profile information to each of the multiple fork registered serving-call session control function; each of the multiple fork registered serving-call session control functions responding by signalling the interrogating call session control function; the interrogating call session control function responding by signalling the proxy call session control function and releasing registration information; and the proxy call session control function responding by creating security associations and storing a list of the multiple fork registered serving-call session control functions.

10. The non-transitory computer readable medium as set forth in claim 9 , the computer program instructions further comprising: the single subscriber user equipment using an algorithm to choose one of the security associations with proxy call session control function and its associated registered serving-call session control function in response to an outgoing call from the single subscriber user equipment.

11. The non-transitory computer readable medium as set forth in claim 10 , the computer program instructions further comprising: if one of the multiple fork registered serving-call session control functions is determined by the single subscriber user equipment or the proxy call session control function to be unavailable for the outgoing call; the single subscriber user equipment choosing an alternative one of the security associations to reach an alternate forked registered serving-call session control function.

12. The non-transitory computer readable medium as set forth in claim 9 , the computer program instructions further comprising: the interrogating call session control function using an algorithm to choose one of the multiple fork registered serving-call session control functions in response to an incoming call to the single subscriber user equipment.

13. The non-transitory computer readable medium as set forth in claim 12 , the computer program instructions further comprising: if one of the multiple fork registered serving-call session control functions is determined by the interrogating call session control function to be unavailable for the incoming or an outgoing call; the interrogating call session control function choosing an alternative one of the multiple fork registered serving-call session control functions.

14. An internet protocol multimedia subsystem network for managing multimedia services that enables single subscriber user equipment to fork register with multiple servinq-call session control functions, the internet protocol multimedia subsystem network comprising: a single subscriber user equipment; a home subscriber server for managing operation of the single subscriber user equipment including a field indicating whether the single subscriber user equipment is enabled for multiple serving-call session control function operation; and multiple serving-call session control functions adapted to accept, in cooperation with the home subscriber server, fork registration from a single subscriber user equipment; wherein the internet protocol multimedia subsystem network is adapted to respond to incoming and outgoing calls to/from the single subscriber user equipment, upon the single subscriber user equipment fork registering with the multiple serving-call session control functions, by choosing one of the multiple registered serving-call session control functions in cooperation with the stored fork registration information associated with the single subscriber user equipment.

15. The internet protocol multimedia subsystem network as set forth in claim 14 , wherein the internet protocol multimedia subsystem network is adapted to use an alternative one of the multiple registered serving-call session control functions if one of the multiple registered serving-call session control functions is unavailable for an incoming or an outgoing call.

16. The internet protocol multimedia subsystem network as set forth in claim 14 , further comprising a proxy call session control function and an interrogating call session control function, wherein the home subscriber server is adapted to return eligible serving-call session control functions to the interrogating call session control function which chooses the eligible serving-call session control functions for registration as the multiple registered serving-call session control functions.

17. The internet protocol multimedia subsystem network as set forth in claim 16 , wherein the single subscriber user equipment is adapted to choose one of the security associations with the proxy call session control function to utilize for an outgoing call using a process from a group consisting of: a random choosing process, prioritized or weighted process and a process based on serving-call session control function capacity.

18. The internet protocol multimedia subsystem network as set forth in claim 16 , wherein the interrogating call session control function is adapted to choose which of multiple registered serving-call session control functions to utilize for an incoming call using a process from a group consisting of: a random choosing process, a prioritized or weighted process and a process based on serving-call session control function capacity.